This won't create an application. It just automates calculations that populate form fields. That's the easy part of most applications. The hard parts are the business logic that isn't just figuring out the values for form fields. In addition, you have nasty cascade effects. What happens in this system when the price for an item changes at the same time the customer's changing the number of that item they want to order, the customer's credit limit is being updated and payments are being applied to his 26 orders each of which causes an update to his balance due? You end up with a massive cascade of updates propagating up the chain, with each change causing changes to values that depend on it which in turn cause yet more changes. Multiply that by thousands of customers and it can kill the systems dead. Meanwhile a non-RP system will handle it cleanly and without dying by simply not updating values until everything's finalized. So as the accounts payable system applies payments to his 26 invoices his balance doesn't change, then when payments are done it updates the balance once to reflect the payments.
I'd use RP to help with things like forms where I want live updates and RP will help automate what I need done anyway. Lots of other areas... not so much. It'd be just another tool in the toolbox, and it's not quite as useful in the real world as it appears in simple academic examples.
Part of it's that the people describing these things often haven't dealt with truly large, complex applications before. Simple example: we have 5 fields in a request, each data file has a match value for each of those fields, and we want to grab the file that matches any one of the fields in the current request. "The" file? Um, what happens when I have 3 files each of which matches a different field of the request? Which one should be grabbed? Nobody thought of that. They say "It doesn't matter, just grab one.". And then later "We wanted file 17 that matched field 3 being X, why aren't we getting that file?", answer "Because file 9 matches when field 1 is A, which it is in your request, and we find file 9 first when checking.". Simple request, just grab an arbitrary file. Translated into the real world, complications pile up that were always there but nobody wanted to talk about because they were... well, complicated.